Bump go version to 1.11

[LucasRoesler]

Description

• Bump the docker go version to 1.11. This helps keep the project up to
  date.

Motivation and Context

• I have raised an issue to propose this change (required)

Rsolves #53

How Has This Been Tested?

• This was tested by building the image, and then deploying the swarm
  stack with authentication disabled. I then deployed a function,
  invoked it, and deleted it via the gateway UI. All actions worked
  as expected

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)

Checklist:

• My code follows the code style of this project.
• My change requires a change to the documentation.
• I have updated the documentation accordingly.
• I've read the CONTRIBUTION guide
• I have signed-off my commits with git commit -s
• I have added tests to cover my changes.
• All new and existing tests passed.

[alexellis]

Thanks!

If CI is happy, please can you bump the ARM files too?

I also saw gofmt was missing on 1-2 files

Alex